1. Field
Embodiments disclosed herein generally relate to a magnetic disk device employing a heat assisted magnetic recording (HAMR) head.
2. Description of the Related Art
Higher storage bit densities in magnetic media used in disk drives have reduced the size (volume) of magnetic bits to the point where the magnetic bit dimensions are limited by the grain size of the magnetic material. Although grain size can be reduced further, the data stored within the magnetic bits may not be thermally stable. That is, random thermal fluctuations at ambient temperatures may be sufficient to erase data. This state is described as the superparamagnetic limit, which determines the maximum theoretical storage density for a given magnetic media. This limit may be raised by increasing the coercivity of the magnetic media or by lowering the temperature. Lowering the temperature may not always be practical when designing hard disk drives for commercial and consumer use. Raising the coercivity, on the other hand, requires write heads that incorporate higher magnetic moment materials, or techniques such as perpendicular recording (or both).
One additional solution has been proposed, which uses heat to lower the effective coercivity of a localized region on the magnetic media surface and writes data within this heated region. The data state becomes “fixed” once the media cools to ambient temperatures. This technique is broadly referred to as HAMR, which can be applied to longitudinal and perpendicular recording systems as well as “bit patterned media”. Heating of the media surface has been accomplished by a number of techniques such as focused laser beams or near-field optical sources.
Typically, external optoelectronic devices such as lasers or photodiodes are integrated into a finished slider through optical coupling to various waveguides that then guide and focus the light onto a plasmonic near field transducer (NFT) used to generate the heat spot. A protective overcoat made of amorphous diamond-like carbon (DLC) is typically formed on the slider facing the magnetic media. Degradation or oxidation of the protective overcoat, along with back-heating of the NFT as a result of slider-media frictional heating, can reduce the reliability of the NFT.
Therefore, an improved method for forming a HAMR head is needed.